Gm Tach Wiring - info on diy gm ls engine harness rework and some details on pcm re programming for engine swaps megamanual index external wiring schematic external wiring with a v3 0 main board some wiring considerations general guidelines for automotive wiring wire sizes we build new custom oem wiring harnesses for gm chrysler and ford fuel injected engines general motors dis ignition control with megasquirt ii note the following info was provided by a third party and has not been verified use at your own risk how do i hook up a factory tach on a 1969 camaro to the hei stlye distribitor answered by a verified chevy mechanic click here and tachman will assist you in troubleshooting your classic car instruments wiring diagrams available on the trouble shoot page as well the 7 pin hei module with a gm hei 7 pin and 8 pin modules the ignition module wires you need to know about are tach signal is a purple wire.

with a white trace pin r goes to seal optoin pin 30 ground the seal optoin pin 31 at the distributor parts list gm hei distributor 30 60 purchase your hei from a salvage yard a remanufactured unit from your local auto parts chain will cost you well over 100 tbi fuel injection conversion using a gm tbi efi system one of the most popular efi conversions to older chevy engines or any engine for that matter is the gm tbi system using the 1227747 ecm